The invention relates to improvements in machines for brewing hot beverages by contacting a flavoring agent (such as comminuted coffee beans, tea leaves or pulverized chocolate) with a heated liquid (such as water or milk).
It is well known to provide a coffee or tea making machine with a housing for a container which can store a supply of fresh water, for a heater which raises the temperature of water to a desired value, for a holder which can receive a supply of flavoring agent (e.g., in a customary bag of filter paper), for a riser which supplies hot liquid from the container to the holder, and for various electrical and electronic components including an on-off switch, one or more signal lamps and/or others. The holder discharges a trickle of freshly brewed beverage into a vessel (e.g., into a coffee pot or tea pot) which can be placed onto a warmkeeping plate in order to maintain the temperature of the beverage at a desired value. Reference may be had to numerous types of coffee and tea makers which are produced and distributed by the assignee of the present application.
Automatic electric coffee and tea makers operate quite satisfactorily and are of considerable help in households as well as in offices and in commercial establishments which sell hot beverages. Moreover, such makers can automatically brew requisite quantities of hot beverages with little or no attention on the part of a person in charge. Thus, all that is necessary is to introduce a selected quantity of fresh liquid and a corresponding quantity of flavoring agent and set the machine for automatic operation.
However, hardly any automatic coffee or tea makers receive high marks as concerns the quality of brewed beverages. Tests with automatic brewing machines indicate that the ratings they receive are invariably below "very good". The main reason is that, with reference to automatic coffee makers, the aroma of coffee which has been brewed in an automatic machine is inferior to the aroma of hand brewed coffee (the term "hand brewed coffee" is intended to denote coffee which is brewed by hand, namely by pouring boiling water over a supply of comminuted coffee beans). This can be explained as follows:
When a hot liquid (such as water in the case of making hot coffee) is poured over a supply of comminuted coffee beans, the person in charge of pouring can readily ascertain whether or not the water has been heated to the boiling point. On the other hand, the temperature of heated water which is caused to contact a supply of comminuted coffee beans in an automatic coffee maker is between 85.degree. and 95.degree. C., i.e., invariably below and often well below the boiling point.
Furthermore, the foremost part of the stream of heated water which reaches the supply of comminuted coffee beans in an automatic coffee maker is relatively cold. The reason is that such foremost part of the stream of hot water exchanges some heat with the conduit (such as a riser) which conveys hot water to the holder for a bag of filter paper. As a rule, water in an automatic coffee maker is heated by an electric heater of the type known as flow-through heater, i.e., the stream of water which is permitted or caused to leave the container for fresh water flows through a conduit a certain length of which is heated from the outside and which discharges heated water into a riser serving to convey heated water to the holder for a supply of comminuted coffee beans. Therefore, many known automatic coffee makers must be equipped with specially designed means for preventing the admission of cold or tepid water into the holder during the initial stage of a brewing operation. However, such means cannot ensure that the temperature of the front part of the stream of heated water will actually reach the boiling point. This is in contrast with the making of hand brewed coffee which invariably involves, or can invariably involve, pouring of boiling water over a selected quantity of comminuted coffee beans.
In addition, when making hand brewed coffee, the container for heated water is invariably (or at least in most instances) a pot or a like vessel which is made of a tasteless material, namely a material which does not adversely influence the aroma and/or other desirable characteristics of the freshly brewed beverage. Such materials include, among others, porcelain, glass, earthenware, ceramics and the like. A person who knows how to brew high-quality coffee is not likely to employ aluminum or copper pots for the heating of water which is to be poured over a supply of comminuted coffee beans. Therefore, the implement which is used to confine water during heating and during pouring of boiling water over comminuted coffee beans will not adversely affect the aroma, color and/or other desirable characteristics of the beverage. On the other hand, the majority of automatic coffee makers employ metallic parts, especially aluminum parts, as a means for confining and guiding water preparatory to, during and after heating. Moreover, the vessels which receive a freshly brewed beverage often consist of or contain metallic materials which are contacted by the beverage. It has been found that the aroma of coffee is affected by contact of water or coffee with metallic parts, especially with parts which contain or are made of aluminum. For example, the conduit which conveys water from the container for fresh water through an electric heating unit in a standard coffee maker is normally made of aluminum. This exerts an adverse influence upon the desirable characteristics of freshly brewed coffee.
Still further, the filtering stage of a hand brewing operation is normally shorter but much more intensive than in an automatic coffee maker. The reason is that the pouring of boiling water by hand is normally a short-lasting operation but the rate of pouring is much higher than in a coffee maker. Therefore, hand pouring does not result in dissolution of bitter tasting constituents of comminuted coffee beans. On the other hand, such constituents are dissolved and leave the holder for the bag of filter paper with the freshly brewed beverage which is obtained in an automatic coffee maker.